Fluid flow transfer devices such as dialyzers are used to continuously remove impurities from a patient's blood. The blood is typically pumped through tubes and arterial and venous bubble traps of disposable tubing sets connecting the patient to a dialyzer mounted on a dialysate preparation and supply machine.
Bellotti et al. U.S. Pat. No. 4,263,808 discloses, as a tubing set replacement, a one-piece hydraulic circuit that includes arterial and venous bubble trap chambers in which blood enters at entrances above the bottoms of the chambers and leaves near the bottoms of the chambers. Pressure in the chambers can be determined by transducers placed against impermeable latex membranes covering holes communicating with upper portions of the chambers.